Regarding a semiconductor manufacturing process in recent years, processes such as multiple exposure and spacer patterning are mainly performed due to the limit of miniaturization by optical lithography. In such a spacer patterning process represented by multiple exposure or SADP (Self Aligned Double Patterning), the number of etching steps increases.
A slight degradation in uniformity of etching performance within a surface of a sample such as a semiconductor wafer to be processed in accordance with each etching step is accumulated due to an increase in the number of etching steps and hence slight degradation of in-plane uniformity is not also easily allowed as the number of steps increases.
Therefore, in the semiconductor manufacturing process represented as the newest logic, particularly, a FEOL (Front End of Line) process, there has been a demand for apparatus performance capable of etching a surface of a substrate to be processed with high uniformity.
In a microwave plasma etching apparatus, a reactor, an evacuation structure, a plasma axial symmetry technology, a wafer placement electrode temperature control technology, and the like are used as a method of realizing the above-described uniformity.
As a related art for obtaining a uniform process distribution inside a substrate, a method of obtaining a uniform plasma density distribution by a high-frequency electric field distribution control disclosed in Japanese Patent Application Laid-Open No. 2-312227 (PTL 1) and Japanese Patent Application Laid-Open No. 8-288259 (PTL 2) is known.
PTL 1 discloses a technology of improving a sample etching speed by increasing an electron temperature of plasma inside a processing chamber in such a manner that a value of a current supplied to a coil forming a magnetic field is periodically increased or decreased in synchronization with a periodical increase or decrease in intensity of a microwave generated by a magnetron in order to realize a pulse discharge forming plasma inside the processing chamber.
Further, PTL 2 discloses a technology provided with a high-frequency antenna wound on the outside of a chamber and a solenoid coil connected to a DC power supply via a switch. Specifically, the technology alternatively forms helicon plasma and inductively coupled plasma by periodically allowing or prohibiting the supply of a DC current to the solenoid coil by the switch while supplying an electric field from the high-frequency antenna into the chamber and freely changes the density of the plasma by controlling a transportation of the plasma toward a substrate disposed below the chamber or an ion/radical generation ratio in the plasma in a desired way.